The general technique of stimulating via implanted electrode arrays is known from various disclosures, such as U.S. Pat. No. 4,532,930 to Crosby et al; U.S. Pat. No. 4,207,441 to Ricard et al; and U.S. Pat. No. 4,611,598 to Hortmann et al. Such techniques generally involve implanting an electrode array into the cochlea to produce a sensation of hearing, connecting the array by direct or indirect means to a stimulation device, and modulating the stimulations in accordance with a signal. This signal is generally produced by processing in some fashion the electrical output of a microphone.
Many known processing techniques concentrate on utilising models of how the sensation of sound is detected by the brain in response to particular stimuli. Thus, the data is processed to some extent with the object of emphasising particular sorts of information in the stimulation of the electrode array.
In a paper by Wilson et al., Processing Strategies for Cochlear Implants, published in 1988, a processing strategy is disclosed utilising a bank of 4 or 6 bandpass filters, the largest 2 or 4 amplitudes in the defined channels being used as the basis for stimulation. The paper states that using more channels, and selecting more channels from the larger set of channels, will improve performance of the processing strategy. There is no discussion of a preferred number of channels, or of how to choose an appropriate number of channels to select, in the case of more than 6 channels being provided by the filter bank.